Gamache earns the displeasure of General Director Francoeur when he ignores his superior's orders and begins investigating the disappearance of Blue Two-Rivers. As a punishment, he's dispatched to the remote village of Three Pines to investigate the murder of a wealthy socialite named CC de Poitiers, where he soon discovers everything is not as it seems and he has no shortage of suspects.

Gamache realises that the key to solving CC's murder lies in her enigmatic past. Discovering that one of the villagers has withheld from him a key piece of information, he is able to crack the case.

Gamache returns to Three Pines to investigate the disappearance of the popular resident Marc Fortier but it soon becomes a murder case that leads Gamache and his team into the heart of the village's dark past at St Anthony's.

The villagers confront the truth of their past and exorcise their collective demons as Gamache makes a breakthrough in the murder case and realises Marc's killer had a very personal motive. Meanwhile, Lacoste makes a discovery relating to Blue's disappearance that seems to identify a key suspect.

The Gamache's anniversary celebrations at the exclusive Manoir Belleforet hotel are cut short by the discovery of a body. Gamache pulls in his team and together they investigate the case, which focuses on the hotel's owners – the dysfunctional Morrow family – who are driven by bitterness and jealousy.

Gamache and his team get to the heart of the case, excavating decades-old resentments and deeply buried secrets in the Morrow family as they do so, and make the key discovery that enables them to identify the killer. Meanwhile, Lacoste's elation at making a breakthrough in the Two-Rivers case proves short-lived and a tragedy leaves her shell-shocked.